Gearless machines such as elevators or other belt-driven systems typically employ a mechanical or electromechanical braking system to stop or temporarily hold a particular motion. Electromechanical brakes of elevators, for instance, generally employ a clutch-type braking mechanism for supplying a holding or braking torque that is sufficient for slowing or holding an elevator cab at a fixed position. The braking torque supplied by clutch-type brakes is mechanically produced by the friction that is generated between a rotating brake disk that is rigidly attached to a machine shaft and a set of friction pads that are releasably placed in contact with a surface of the brake disk. The engagement or disengagement of the friction pads is electromechanically controlled by a brake coil. Moreover, when the brake coil is activated, a magnetic attraction between the armature plates and an electromagnetic core causes the friction pads to disengage from the surface of the brake disk. When the brake coil is deactivated, springs that engage the armature plates urge the armature plates into engagement with the surface of the brake disk. Although such clutch-type brakes may have been proven to be effective and are still widely used in various gearless applications such as elevators, and the like, there is still room for improvement.
Due to its dependency on friction, clutch-type brakes can be noisy. The braking performance is also dependent on environmental factors, such as temperature, humidity, and the like. For instance, in moist environments, the friction pads of clutch-type brakes may stick to the brake disk. Furthermore, the range of braking torque that a specific clutch-type brake can variably apply is relatively narrow. For example, a clutch-type brake cannot provide enhanced or sufficiently more stopping power for emergency stops, or the like. Conversely, a clutch-type brake cannot provide reduced stopping power for normal stops than with emergency stops. A typical clutch-type brake is limited to its rated torque which is further dictated by the invariable mechanical limits of the brake, material composition of its friction pads, and the like. Accordingly, it follows that clutch-type brakes offer less overall control or variation of the braking torque.
The manufacturing and installation of clutch-type brakes onto the frame and shaft of an elevator can be complex and costly. Correspondingly, making adjustments to a pre-existing clutch-type braking system may also be costly and difficult to perform. Regardless of the degree of maintenance performed, however, long-term use of clutch-type brakes could result in burnished surfaces on bearing frames, splinted shaft ends, and the like. Furthermore, the very nature of clutch-type brakes calls for a substantial number of moving parts and components, which indicates yet another area having room for improvements. For instance, clutch-type brakes as applied to elevators may require several mechanical springs, O-rings, guiding pins, and the like.
Clutch-type brakes may also use proximity sensors, micro-switches, or the like, to indicate the status of the brake or to provide feedback of the performance of the brake. Furthermore, the pure mechanical nature of clutch-type brakes makes it difficult to integrate the brake with any other useful controls or functions, such as speed detection, position detection, rescue encoding, or any other subsystem functions.